data limit in Mikrotik with Freeradius and Mysql

Hi Does anyone have solution for limiting users with data traffic. I have working setup of Mikrotik with freeradius and mysql. Have searched on net and found one solution but I can put limit to max 4 GB data. After 4 GB the counter resets to 0. I know the reason of that. It's b'coz of the values stored in protocol are 32 bits only. Awaiting your reply. Thanks & Regards, Ravin